The present invention relates to valves used for controlling the flow of fluidized solids in applications where the fluidization may be lost and static solids may accumulate. It is particularly well adapted for use in processes for the gasification or liquefaction of coal or other solid carbonaceous fuels or in processes for the fluidized bed combustion of such material.
The flow of finely divided solids is conveniently controlled in the unfluidized state with mechanical feeders, e.g. reciprocating or rotating conveyors or with valves having translating, rotating or sliding closure plates. However, in systems having extreme environments that must be well contained, such as in high temperatures, pressures or with corrosive materials, these conventional devices for maintaining a metered flow of solids are unsuitable or extremely inconvenient.
Various commercially available valves include pivoted or rotatable closure members that can be operated to present wide openings for solids flow. One such device is known as a trickle or flapper valve that includes a hinged closure plate that can be biased in the closed position by back pressure. A valve of this type provides poor flow control of solids as they tend to clog the flow channel and a small valve movement produces a large flow area. Where a pressure differential is used for biasing, the opening of the valve can actually produce an upward gas flow to restrict the desired solids release.